I advise you to read Project Oberon from Niklaus Wirth, originally published in 1992, revised in 2013 for targeting a FPGA instead of the Ceres workstation that was used at Zurich Institute of Technology (ETHZ) during the 90's.
A complete graphical workstation OS used by the IT department for their OS programming classes, language design and even by the non technical personal at the department.
I advise you to read Project Oberon from Niklaus Wirth, originally published in 1992, revised in 2013 for targeting a FPGA instead of the Ceres workstation that was used at Zurich Institute of Technology (ETHZ) during the 90's.
https://people.inf.ethz.ch/wirth/ProjectOberon/index.html
http://www.ocp.inf.ethz.ch/wiki/Documentation/Front
A complete graphical workstation OS used by the IT department for their OS programming classes, language design and even by the non technical personal at the department.